With popularization of cloud technologies, the cloud technologies are used for increasingly more telecommunications-type services. Network functions virtualization (NFV) is a virtualization technology in the cloud technologies. In an NFV system, a virtualized network function (VNF) is instantiated, so that the VNF can run on a universal hardware device. Therefore, a specific network function is implemented using the universal hardware device.
In the NFV system, one VNF may be configured on one or more virtual machines. Hot migration is often performed on a virtual machine to satisfy different user requirements. Virtual machine hot migration refers to transferring, if a service is not interrupted, a virtual machine that runs on one hardware device to another hardware device for running. However, in a virtual machine hot migration process, a virtual machine stops running in an extremely short time. Consequently, a system time of the virtual machine pauses for a short time that is usually 0.5 to 0.8 second and sometimes reaches more than 1 second. In this way, a service depending on the system time of the virtual machine is affected.
In the prior art, an exterior Network Time Protocol (NTP) system time source is usually configured, and a system time of a virtual machine is periodically checked with the exterior NTP system time source, to correct the system time of the virtual machine. However, a problem exists in that generally, a period of periodically checking the system time of the virtual machine with the exterior NTP system time source is five minutes, 10 minutes, or a longer time, and the system time of the virtual machine is inaccurate in a period of time from a time at which the virtual machine stops running to a time at which the foregoing period expires. Therefore, a service that depends on the system time of the virtual machine and that is performed in the period of time is affected.